This invention relates to an apparatus for compacting earth. More particularly, this invention relates to an apparatus for compacting earth in trenches and the like.
At the present time there are several different types of machines that are used to compact earth. One type of machine that is frequently used is what is known in the trade as a sheepsfoot. An example of a sheepsfoot may be found in U.S. Pat. No. 3,183,804. Although the sheepsfoot has proven to be an effective low cost per yard approach to surface compaction its usefulness in trench line compaction has never been fully realized.
In U.S. Pat. No. 2,146,101 is disclosed an apparatus for compacting earth in trenches. The apparatus includes a sheepsfoot connected to a pulling vehicle by a coupling assembly such that it can be towed by the pulling vehicle but not raised or lowered or moved from side to side of the pulling vehicle.
In U.S. Pat. No. 3,471,953 is disclosed an apparatus for compacting earth in trenches which includes a sheepsfoot positioned centrally of a pulling vehicle such that the pulling vehicle must straddle the trench at all times.
Other types of sheepsfoot apparatus are disclosed in U.S. Pat. Nos. 3,136,078; 3,183,804; and 2,437,524. Other types of machines for compacting earth are disclosed in U.S. Pat. Nos. 2,732,197 and 2,852,992.
In U.S. Pat. No. 3,024,546 is disclosed an apparatus for digging ditches which includes a ditcher head that is mounted for lateral and vertical movement. In the apparatus, the adjustable ditcher is spaced laterally to the right of the tread of the tractor with the tractor moving forward. There are several shortcomings to such an apparatus. Firstly, it is not an earth compacter, but more importantly, the operator can not readily shift to the opposite side or place his ditcher anywhere between the tread lines.
Such shortcomings are not found in the apparatus of this invention. In addition, this invention can be employed without the need to add additional fill dirt as would seem to be taking place at all times in the apparatus in U.S. Pat. No. 3,471,953.
The present invention relates primarily to the field of underground utility work; that is, the laying of pipe or wires in trenches. The steps involved in such a project include site preparation, trenching, laying of pipe or wire, backfill, compaction and site restoration. All aspects of the total task, with the exception of compaction have advanced rapidly to a high degree of sophistication in recent years.
The compaction step is in fact a plurality of steps which include preparatory compaction of the trench bottom, the compaction of material in and around the pipe or wires and the compaction of the trench above the newly laid pipe or conduit. The ability to produce work that meets specification and yet be monetarily productive has lagged with the advent of more strigent requirements of O.S.H.A., as well as the advances made in other aspects of the total job. This has resulted in a disproportionate cost in compaction in relation to the work as a whole.
Furthermore, all field backfill work is governed by soils laboratory measured achievable compaction using precise measurements of weight, moisture and expended effort for controlled test cores, with the result that actual field requirements are related as a percentage of laboratory results, and are called out as relative density, i.e. the field density test is relative to the laboratory test core.
In the present state of the art there are basically five different mechanical modes of attempting to achieve the desired field densities.
The most common is the gasoline powered, stomping type of unit or whacker, which is operated by one man, which is designed for use on relatively flat small area surfaces and which requires the operator to follow the machine into the trench.
Another common unit is the hydraulic backhoe mounted Hoe-Pac. This type of device is basically a vibrated plate. The chief handicap of such a device is its inability to produce a continuous effort, and the necessity of the prime mover, i.e. the tractor, to straddle the trench, which is not always safe or even possible.
Other known devices used are the dual drum self-propelled roller, as made and sold by Duomat, Mikasa and otheres; and the drop hammer type of unit as made by Arrow Champion and others. The dual drum roller suffers the shortcomings of the wacker. The drop hammer which must also straddle the trench, requires the trench to be jetted, a term known to the art, for it to be effective. Ofttimes only the upper area meets the relative density compaction, specification, while the deeper areas do not. Also there is the danger of pipe floating during the jetting operation.
The vibratory sheepsfoot has in recent years been recognized as an effective low cost per yard approach to compaction. However, prior use has been limited to surface compaction on surfaces up to about 6' in width and large diameter pipelines, because there was no way of utilizing it within a trench of the size used in normal pipeline operations. The invention of this application allows a narrow vibratory sheepsfoot to be employed in a backfill trenching operation with dramatic results both in productivity and safety to the workmen.